Wind Generators.

Riin MaripuuKristiina Purga

12c

Humans have been using wind power for at least 5,500 years to propel sailboats and sailing ships, and architects have used wind-driven natural ventilation in buildings since similarly ancient times. Windmilles have been used for irrigation pumping and for milling grain since the 7th century AD.

The modern wind power industry began in 1979 with the serial production of wind turbines by Danish manufacturers Kuriant, Vestas, Nordtank, and Bonus.

These early turbines were small by today's standards, with capacities of 20–30 kW each.

Since then, they have increased greatly in size, while wind turbine production has expanded to many countries.

Advantages of wind energy Attractive as an alternative to

fossil fuels. It plentiful, renewable, widely

distributed, clean, and produces no greenhouse gas emissions.

Wind turbines locations with constantly high wind speeds bring best return on investment.

It is not politic to build wind generators to places with wind speed under 6m/s.

A quantitative measure of the wind energy available at any location is called the Wind Power Density (WPD.)

It is a calculation of the mean annual power available per square meter of swept area of a turbine, and is tabulated for different heights above ground. Calculation of wind power density includes the effect of wind velocity and air density.

There are several wind farms with horizontal turbines in Estonia that belong to different companies and private ownership. Some of the biggest are listed here:

*Virtsu 1 wind farm *Virtsu 2 wind farm *Pakri wind farm *Paldiski wind farm *Viru-Nigula wind farm *Kunda wind-farm *Sudenai wind farm *Hiiumaa offshore wind farm

Right now there are expansions and developments in the making.

It is planned for the wind energy power level to increase to 700…2100 MW

Horizontal axis advantages Variable blade pitch, which gives

the turbine blades the optimum angle of attack, so the turbine collects the maximum amount of wind energy for the time of day and season.

The tall tower base allows access to stronger wind in sites with wind shear. In some wind shear sites, the wind speed can increase by 20% and the power output by 34% for every 10 metres in elevation.

Horizontal axis advantages High efficiency, since the blades always move perpendicular to the

wind, receiving power through the whole rotation. The face of a horizontal axis blade is struck by the wind at a

consistent angle regardless of the position in its rotation. This results in a consistent lateral wind loading over the course of a rotation, reducing vibration and audible noise coupled to the tower or mount.

Horizontal axis disadvantages The tall towers and blades up to

90 meters long are difficult to transport. Transportation can now amount to 20% of equipment costs.

Tall HAWTs are difficult to install, needing very tall and expensive cranes and skilled operators.

Massive tower construction is required to support the heavy blades, gearbox, and generator.

Horizontal axis disadvantages Reflections from tall HAWTs may affect side lobes of radar installations

creating signal clutter, although filtering can suppress it. Their height makes them obtrusively visible across large areas, disrupting

the appearance of the landscape and sometimes creating local opposition.

Downwind variants suffer from fatigue and structural failure caused by turbulence when a blade passes through the tower's wind shadow (for this reason, theAmajority of HAWTs use an upwind design, with the rotor facing the wind in front of the tower).

HAWTs require an additional yaw control mechanism to turn the blades and nacelle toward the wind.

Thank you!